The present invention relates generally to shields used in the protection of electronic components from electromagnetic and radio frequency interference and more specifically, relates to radio frequency (RF) shields mounted on printed circuit boards and the like.
Electronic components, such as resistors, capacitors, and semiconductor components, are often subjected to undesirable emissions, such as electromagnetic and radio frequency interference, from neighboring components that emit such interference. The emitted interference adversely impacts the performance and integrity of the electronic components as these emissions interfere with the operation of the electronic components by temporarily altering or distorting their essential characteristics, which thus leads to adverse performance.
Several methods are available for protecting and shielding one or more electronic components from the electromagnetic and radio frequency interference which is occurring in the proximate vicinity of the electronic component, e.g., a printed circuit board (PCB). One method of protecting an electronic component from such emissions is to provide a shield which serves to shield an area of the printed circuit board(s), or a volume associated therewith. The shield functions by either containing electromagnetic energy, e.g., radiated RF signals, within a shielded volume or area or the electromagnetic energy is excluded by the shield structure from the shielded volume or area.
Such shielding is extensively used in television receivers, direct satellite broadcast receivers, radio receivers such as FM and shortwave, or portions of audio systems, wherein low signal level circuitry is amenable to being effected by stray electromagnetic fields emanating from AC power sources.
A printed circuit board (PCB) is a common electronic component to which a shield can be applied since PCBs enjoy widespread use in a number of electronic applications. The term xe2x80x9cprinted circuit boardxe2x80x9d generally refers to circuit boards having electrical conductors disposed on one or more side of a substrate (e.g., a dielectric substrate). Often a PCB will have openings or the like formed through the substrate to receive electrical leads of an electronic component that is mounted on one side of the PCB. The electrical leads extend through the openings to contact pads disposed on the other side of the PCB. The leads are typically soldered to the contact pads.
There are several techniques for mounting the shield to the PCB. One technique is to directly solder the shield to a ground plane of a PCB that is proximate to electromagnetic and radio frequency emitting components. Another technique involves the use of shield clips coupled to the ground plane of a PCB to which a shield is permanently attached. Another technique involves the use of removable shields attached to shield clips coupled to the ground plane of the PCB.
There are several disadvantages associated with the above-recited techniques. One disadvantage is that it is often time consuming to solder the shield to the ground plane of the PCB. This results in increased manufacturing cost. Another disadvantage is that it can be cumbersome to apply the solder to the shield and then join the shield to the ground plane.
Accordingly, it is desirable to provide a solderable shield that can easily and effectively be soldered to a portion of an electronic component, such as a PCB.
An electromagnetic shield is provided and includes a shield body having an outer wall. The outer wall has a plurality of resilient fingers formed at a lower edge thereof. The electromagnetic shield also includes a solder mass securely held by the fingers by being interleaved between the fingers. The interleaving of the solder mass results in the solder mass being securely held by the fingers and ready for mounting to an electronic component for shielding a portion of the electronic component from undesirable and potentially damaging emissions from neighboring components.
A method of mounting an electromagnetic shield to an electronic component having a planar surface is also provided. The electromagnetic shield has a shield body that it typically open on one face thereof and which defines an interior space. The method includes the steps of (a) forming a plurality of fingers in the electromagnetic shield, wherein the fingers are formed at a lower edge of electromagnetic shield and each finger is defined by a pair of slots formed in the electromagnetic shield on each side of the finger; (b) interleaving a solder mass between the fingers such that the solder mass is securely held by the fingers; (c) disposing the electromagnetic shield on the planar surface of the electronic component so that a predetermined section of the electronic component is disposed within or underneath the interior space of the shield; (d) reflowing the solder mass; and (e) cooling the reflowed solder mass so as to provide a secure solder connection between the shield and the electronic component.
According to one embodiment, the step of interleaving the solder mass includes the steps of (a) bending a first set of the plurality of fingers in a first direction; (b) bending a second set of the plurality of fingers in a second direction, thereby forming a channel between the bent first and second set of fingers; (c) disposing the solder mass within the channel; and (d) bending the first set of fingers in the opposite second direction and bending the second set of fingers in the opposite first direction so as to cause the solder mass to become interleaved between the first and second set of fingers.
The interleaving of the solder mass at a lower edge of the electromagnetic shield provides an effective yet easy manner of securely retaining the solder mass before and during a mounting operation where the electromagnetic shield is securely mounted on an electronic component, such as a printed circuit board (PCB) so as to shield certain sensitive areas of the electronic component from emissions generated by neighboring components.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.